There may be some circumstances when there is a need to measure the speed of an elevator car moving through a hoistway. For example, some needs may be during elevator installation or maintenance. Conventionally, an elevator technician or mechanic climbs on top of the cab and utilizes a hand-held tachometer to check the speed of the elevator during adjustment or testing. This technique typically requires the technician to hold the tachometer against one of the guide rails within the hoistway while simultaneously attempting to run the elevator using the top of car inspection box. While this technique does provide speed information, there are limitations.
Some limitations can include efficiency and accuracy of the speed measurement are sometimes compromised because of the technician's capabilities for maintaining contact between the tachometer and the guide rail with one hand while operating the top of car inspection box with the other hand. Additionally, there are serious safety concerns any time that a technician is required to be on top of an elevator cab while it is moving through the hoistway.
U.S. Pat. No. 5,896,949 describes an elevator installation, in which the ride quality is actively controlled using a plurality of electromagnetic linear actuators. This active ride control system provides for an elevator car to travel along guide rails in a hoistway, wherein sensors mounted on the elevator car measure vibrations occurring transverse to the direction of travel. Signals from the sensors are input to a controller which computes the activation current required for each linear actuator to suppress the sensed vibrations. These activation currents are supplied to the linear actuators which actively dampen the vibrations and thereby the ride quality for passengers traveling within the car is enhanced. The controller comprises a position controller with position feedback, which is problematic for many reasons. For example, the position feedback controller is rather slow and the controller output is limited to a level to not cause overheating of the actuators. Further problems include that the output from the acceleration controller, is not restricted and thus produces large amplitude resonance forces at the actuators. Resulting in all closed loop controllers to become unstable if feedback gain is too high.
Therefore, a need exists in the art for an improved way to estimate motion of an elevator car of an elevator system that includes measuring one or a combination of speed and vibration of the elevator car within the elevator system for controlling the operation of the elevator system.